Necessity of Cooling Aeroplane At Higher Altitude While Temperature at Higher Altitude is Lower Than Ground ?

            Temperature at higher altitude is low as compare to ground thereafter it is necessary to cool the aeroplane because due to many external and internal heat source, temperature of passenger cabin get increased (for comfort feeling temperature of passenger cabin must be approx 22℃ to 24℃) and for the prevention of passenger foods & drink lower temperature is required (approx 5℃).

Major source due to which compartment is heated

External Source

• Sun - Sun pours a heavy quantity of heat in the passenger cabin through the window and also heat the top surface. 

• Air - When a fast-moving plane passes through air, then viscous force is generated by air due to which high temperature is generated between aeroplane surface and air near to surface which causes a heating of the surface. 

• Pressurized Air - Pressure at higher altitude is lower than atmospheric pressure at sea level and the pressure of passenger cabin is required as atmospheric pressure at sea level, for maintain this pressure (atmospheric pressure at sea level) in passenger cabin for this we compressed the ambient air from ambient pressure to atmospheric pressure at sea level and supply to the passenger cabin during this process temperature of air increases so that the temperature of passenger cabin also increased.

Thermodynamics System and Its Type

Internal Source

• Aeroplane engine generates a huge amount of heat during its operation and these heat come to the passenger cabin through conduction, convection and radiation. 

• The electrical equipment which is used to control the system generates heat. 

• The human body continuously generates heat and this heat dissipated to the cabin.